Plans for Developing a Rainwater Cistern or Hauled Water ... - ATSDR

The construction of rainwater cisterns and hauled water storage tanks used as private
water supplies in Ohio is covered in Ohio Administrative Code (OAC) 3701-28-13.
Rainwater cistern and hauled water tank configuration may vary by contractor and do not
necessarily need to correspond with all of the examples provided in this document as long the
cisterns or tanks are constructed in compliance with the Private Water System Rules. Contact
your local health department for the necessary permits and for additional information.
A rainwater cistern is a type of water system that collects rainwater off of a roof and channels it
through gutters to a collection tank for storage until used by the household. Cisterns may also
be referred to as rainwater catchments or rainwater harvesting systems. A hauled water storage
system is not designed to collect water off of a roof but is simply a water tank that is refilled
exclusively by truck deliveries from approved public water supplies. Water haulers must comply
with OAC Rule 3701-28-18 before they can deliver water to private drinking water cisterns or
hauled water storage tanks. Local health departments inspect these water hauling trucks annually
for compliance with OAC Rule 3701-28-18.
Cisterns and hauled water storage tanks may be used where ground water is not available or is
impractical to treat for home use. Cisterns are required to have continuous disinfection in accordance
with OAC Rule 3701-28-07 in order to make the water sanitary for potable uses. Hauled
water storage tanks are not required to have any additional treatment.
Sizing Your Cistern or Hauled Water Storage Tank as a Private Water System
In Ohio the minimum required size of a cistern is 2500 gallons, and the minimum required size
for a hauled water storage tank is 1000 gallons when used as private water systems. However,
the overall size of the tank should be based on the expected water needs of the household. The
ideal storage capacity of the cistern can be calculated based on the longest drought period
within the last 50 years. A safety factor of 25% is then added to that storage capacity.
Ohio receives about 37 inches of rainfall per year. Monthly average rainfall can vary greatly. It
may rain as much as 7 inches in an above normal wet month and as little as zero in other
months. The Hydrologic Atlas for Ohio (1991), Water Inventory Report 28, provides additional
information on average annual rainfall across Ohio for a 50 year period (1931-86). A copy of this
document can be obtained from the Ohio Department of Natural Resources, Division of Water
or at www.dnr.state.oh.us/pubs/hydatlas. Seven inches of rainfall on a 1500 square foot roof will
yield about 6300 gallons. Most of this water would be wasted if the storage capacity of the cistern
were the minimum 2500 gallons. Therefore it is recommended that a cistern to be used as
the primary water source for a year round residence have at least a 6000 gallon to 10,000 gallon
capacity using one or more tanks. It is very likely that a cistern water supply will have to be
supplemented from a hauled water delivery company.
The cistern may also sized based on the following roof areas:
Roof Area in Square Feet Gallons capacity of cistern
Less than 1000 2500 to 5000
1000-1500 7500
1500-2000 10,000
2000 or more 12,500+
1